"What ball"

"Where is your ball" I say to which he gives me this "What ball" look and proceeds to run around in circles pretending to look for it. After a few minutes of me shouting "You know where it is, go and get it" he will take off, usually some distance back the way we have come, and go straight to it.  He has done it too many times not to be a game on his part and usually when he thinks I am taking to long on my blip.
He is a springer spaniel, aged 11 (nearly) and he belongs to me. I think!!!!!